Observed spectrum of the old star CS 31082-001

The observed spectrum (dots) of the old star CS 31082-001 in the region of the uranium (U II) line at 385.96 nm. The origin of some of the other spectral lines in the region is also indicated (e.g. iron, neodymium). The synthetic spectrum (thin line) was computed for the adopted abundances of the stable elements and for four different values of the abundance (by number) of uranium atoms in the atmosphere of the star. The uppermost line (corresponding to no uranium at all) clearly does not fit the observed spectrum at all. The best fit is provided by the middle (red) line, representing a uranium abundance of approximately 6% of the solar value.